Solar cycle 15

Solar activity from July 1913 to August 1923

Solar cycle 15
Sunspots recorded during solar cycle 15 (23 January 1923).
Sunspot data
Start date	July 1913
End date	August 1923
Duration (years)	10.1
Max count	175.7
Max count month	August 1917
Min count	2.5
Spotless days	534
Cycle chronology
Previous cycle	Solar cycle 14 (1902–1913)
Next cycle	Solar cycle 16 (1923–1933)

Solar cycle 15 was the fifteenth solar cycle since 1755, when extensive recording of solar sunspot activity began.^[1]^[2] The solar cycle lasted 10.1 years, beginning in July 1913 and ending in August 1923. The maximum smoothed sunspot number observed during the solar cycle was 175.7 (August 1917), and the starting minimum was 2.5.^[3] During the minimum transit from solar cycle 15 to 16, there were a total of 534 days with no sunspots.^[4]^[5]^[6]

History

Geomagnetic storms in March 1918, August 1919, October 1919, and March 1920 affected telegraph lines, while a solar flare on 13 May 1921 also affected rail signal and switching equipment, in what was known as the "New York Railroad Storm."^[7]

1921

A major geomagnetic storm during 13–15 May 1921 caused damage in communication systems and aurora displays in much of the eastern United States.^[8]

In Sweden, the event caused major disruptions to the telephone exchange in Karlstad and in the early morning of May 15, the building burned down.^[9] Witnesses described the telephone cables going into the building as glowing.

References

^ Kane, R.P. (2002), "Some Implications Using the Group Sunspot Number Reconstruction", Solar Physics, 205 (2): 383–401, Bibcode:2002SoPh..205..383K, doi:10.1023/A:1014296529097, S2CID 118144552
^ "The Sun: Did You Say the Sun Has Spots?". Space Today Online. Retrieved 12 August 2010.
^ SIDC Monthly Smoothed Sunspot Number. "[1]"
^ Spotless Days. "[2]"
^ Dr. Tony Phillips (11 July 2008). "What's Wrong with the Sun? (Nothing)". NASA. Archived from the original on 14 July 2008.
^ Solaemon's Spotless Days Page. "[3]"
^ "Space Weather Newspaper Archives". 28 July 2017.
^ Storms, Solar (28 July 2017). "Space Weather Newspaper Archives". www.solarstorms.org.
^ O'Callaghan, Jonathan. "New Studies Warn of Cataclysmic Solar Superstorms". Scientific American. Retrieved 8 November 2021.

Solar cycles

18th century

1740–1759	Solar cycle 1 (1755 Feb – 1766 Jun)
1760–1779	Solar cycle 2 (1766 Jun – 1775 Jun) Solar cycle 3 (1775 Jun – 1784 Sep)
1780–1799	Solar cycle 4 (1784 Sep – 1798 Apr) Solar cycle 5 (1798 Apr – 1810 Aug)

19th century

1800–1819	Solar cycle 6 (1810 Aug – 1823 May)
1820–1839	Solar cycle 7 (1823 May – 1833 Nov) Solar cycle 8 (1833 Nov – 1843 Jul)
1840–1859	Solar cycle 9 (1843 Jul – 1855 Dec) Solar cycle 10 (1855 Dec – 1867 Mar)
1860–1879	Solar cycle 11 (1867 Mar – 1878 Dec) Solar cycle 12 (1878 Dec – 1890 Mar)
1880–1899	Solar cycle 13 (1890 Mar – 1902 Jan)

20th century

1900–1919	Solar cycle 14 (1902 Jan – 1913 Jul) Solar cycle 15 (1913 Jul – 1923 Aug)
1920–1939	Solar cycle 16 (1923 Aug – 1933 Sep) Solar cycle 17 (1933 Sep – 1944 Feb)
1940–1959	Solar cycle 18 (1944 Feb – 1954 Apr) Solar cycle 19 (1954 Apr – 1964 Oct)
1960–1979	Solar cycle 20 (1964 Oct – 1976 Mar) Solar cycle 21 (1976 Mar – 1986 Sep)
1980–1999	Solar cycle 22 (1986 Sep – 1996 Aug) Solar cycle 23 (1996 Aug – 2008 Dec)